ci/lava: Add LavaFarm class to find LAVA farm from runner tag

LavaFarm is a class created to handle the different types of LAVA farms
and their tags in Mesa CI. Since specific jobs may require different
types of LAVA farms to run on, it is essential to determine which farm
the runner is running on to configure the job correctly.

LavaFarm provides an easy-to-use interface for checking the runner tag
and returning the corresponding LAVA farm, making it simple for Mesa CI
to configure jobs appropriately. By adding tests for LavaFarm, the team
can ensure that this class is functioning as expected, allowing for the
smooth execution of Mesa CI jobs on the correct LAVA farm.

The tests ensure that get_lava_farm returns the correct LavaFarm value
when given invalid or valid tags and that it returns LavaFarm.UNKNOWN
when no tag is provided. The tests use Hypothesis strategies to generate
various labels and farms for testing.

Example of use:
```
from lava.utils.lava_farm import LavaFarm, get_lava_farm

lava_farm = get_lava_farm()
if lava_farm == LavaFarm.DUMMY:
    # Configure the job for the DUMMY farm
    ...
elif lava_farm == LavaFarm.COLLABORA:
    # Configure the job for the COLLABORA farm
    ...
elif lava_farm == LavaFarm.KERNELCI:
    # Configure the job for the KERNELCI farm
    ...
else:
    # Handle the case where the LAVA farm is unknown
    ...
```

Signed-off-by: Guilherme Gallo <guilherme.gallo@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21325>

.gitlab-ci/container/debian/x86_build.sh

@@ -92,7 +92,7 @@ ninja install
 popd
 rm -rf DirectX-Headers
 
-python3 -m pip install -r ${CI_PROJECT_DIR}/.gitlab-ci/lava/requirements.txt
+python3 -m pip install -r .gitlab-ci/lava/requirements.txt
 
 # install bindgen
 RUSTFLAGS='-L native=/usr/local/lib' cargo install \